Differences Between The Drivetrains In Formula E Racers – Video

2 years ago by Mark Kane 20

There was not much differences in the e-drivetrains of the Formula E cars.

 Jaguar Formula E racer

Jaguar Formula E racer

But a recent vidoes shows that among the 9 teams (the 10th has now pulled of the competition for the current year) there are several different approaches on the inverter/motor/transmission, which could lead to advantages for the driver.

Depending on team, the cars use anywhere from single to five gear transmissions. In the case of a single reduction gear, there are also two motors – one on shaft to get high enough torque.

There is still no clear answer which solution is the best, although the two gear transmission (from Renault e.Dams) lead the team standings, followed by Dragon Racing (four gears), ABT Schaeffler Audi Sport (three gears) and DS Virgin Racing Formula E Team (single speed).

By the end of the season we should have a more definitive answer on the most optimized solution, but the unequal number of teams using particular solutions still makes comparisons difficult.

Formula E Cars – What Are The Differences?
Season 2 of Formula E saw the regulations opened up so that each team could develop its own motor, inverter and transmission. Remarkably, given that each team had the same task, the solutions are dramatically different. There are cars on the grid running everything from two motors and one gear to one motor with five gears, and virtually everything in between. Find out the differences between each team’s drivetrain in this informative video.

Team standings after five rounds (out of 11):

1 Renault e.Dams
2 Dragon Racing
3 ABT Schaeffler Audi Sport
4 DS Virgin Racing Formula E Team
5 Mahindra Racing Formula E Team
6 Andretti Formula E Race Team
7 Venturi Formula E Team
8 Team Aguri
9 NEXTEV TCR Formula E Team

 

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20 responses to "Differences Between The Drivetrains In Formula E Racers – Video"

  1. ModernMarvelFan says:

    1 gear isn’t enough for racing at all.

    Despite all the EV knuckleheads’ lack of understanding, even the broad curve of the Electric motors will fall victim to high rpm and efficiency.

    For typical “city car”, 1 gear is sufficient for the sake of cost and simplicity.

    For a well around car, 2 gears will allow efficiency and performance with slightly higher cost and weight.

    Anything more than 3 are un-necessary unless you want to reduce the cost of motor and motor drives.

    Rimac uses 2 speeds on two of the motors..

    1. Djoni says:

      I’d like to see a star delta motor into it.
      That would be a 2 speeds motor without gear.
      Copywright here.

      1. Bill Howland says:

        Star/Delta at the output of an inverter could improve the inverter’s efficiency at low speeds. And Mechanical contactors would be effectively lossless. It allows the voltage to be sqrt(3) higher, so inverter losses are less at low voltages/speeds.

        But that’s a pretty small benefit. I’m sure the smallness of it is why I haven’t seen it used on an EV as of yet, or if they have used it, why it hasn’t caught on.

        1. Djoni says:

          It’s been done:
          http://insideevs.com/jay-lenos-garage-electric-bus-conversions-on-the-cheap/

          Don’t know if they use contactor switching, but I am pretty sure it could be done without it using a properly design multi pole inverter.
          But, the low speed high torque of this configuration might not be a formula E forte.
          It’s a practical solution avoiding heavy transmission.

          1. Bill Howland says:

            Well, to repeat, the bus gets a bit more efficiency at the inverter since it can generate its output at 1.732 times the voltage, and the current can be I/1.732, but there is no change with the motor ( the guy mis-spoke if he’s talking about star/delta – there is no ‘hi/lo’ winding since its all the same wires). And no torque multiplication at the motor. The savings is strictly due to the increased efficiency at low speeds of the inverter – which a 1% or 2% gain is worth doing, but its not an earth-shattering improvement.

          2. Bill Howland says:

            On this bus its not done by a ‘properly designed multi-pole inverter’, since the video clearly shows 3 wires from the inverter output.

            More lossey switching negates the inverter efficiency advantage that is trying to be exploited, so I’d vote for one set of poles per phase, instead of 2 sets of losses, and then take care of the star/delta transition the normal way – for a bus to minimize the jerkiness he said was there, I’d assume a standard ‘closed transition’, eg. with resistors – but open transition would work too since a bus has so much momentum at speed.

      2. ModernMarvelFan says:

        It won’t solve the back EMF issue.

        1. Bill Howland says:

          What ‘Back EMF Issue’?

    2. Will says:

      Was there really any call to be condescending?

      1. ModernMarvelFan says:

        Look at the comment below, you will see why they deserve that tone…

    3. jerryd says:

      The problem with EV transmissions is they break from the massive, instant torque.
      I do like the 2 motors on one shaft with either 2 types or series/parallel them as a 2 speed.
      In my future EVs I’ll use 2 motors series/parallel to get low end torque and high end power.

      1. ModernMarvelFan says:

        “The problem with EV transmissions is they break from the massive, instant torque.”

        REally? Just because Tesla couldn’t do it, others can’t?

        Rimac’s massive torque are even bigger than tesla and they do it just fine.

        The so called “instant torque” can be “instantly adjusted” as needed.

        No need to make up excuses.

  2. GeorgeS says:

    Being an old gear head I’m fascinated by the trade offs. I would think 2 gears max would suffice….It’s a race car so you can splurdge.

  3. Bill Howland says:

    Most of the EV transmission makers say 3 speeds are necessary. Seeing as the only place the volt is somewhat inefficient is at take off, and has a ‘poor man’s’ extra speed when going fast, those guys who say 3 speed transmissions seem about right.

  4. np says:

    Here’s where extra gears would help even the mighty P90D:
    http://www.caranddriver.com/reviews/2015-tesla-model-s-p90d-test-review

    “You hope the rush lasts to orbital escape velocity but, alas, it soon peters out. Roll alongside a Dodge Charger SRT Hellcat at 40 mph, for example, and the Mopar beats the Tesla to 150 mph by more than six seconds.”

    1. arne-nl says:

      How do you know the extra gears would help?

      Most likely the limiting factor for high speed acceleration in a Tesla is in the current draw from the battery and no amount of gears can help you.

      1. np says:

        Given that the current draw will be the same as it is in lower speeds since when you add taller gears, you are stepping down in rpms after the upshift, why should it be the limiting factor?

        Did you think by adding gears means increasing engine speed? I mean exactly the opposite.

        The roughly 10:1 final drive Tesla uses (last I read for P85) can be be instead 5:1 combined with a two-speed tranny with first gear ratio of 2.0. Then you’ll retain the acceleration same characteristics at lower speed, AND upshift and come back into the higher efficiency area of the AC motors again at higher speeds, instead of going past torque peak, and just generating heat as they all do now.

  5. arne-nl says:

    Whether an EV needs a gearbox you need to answer a simple question:: does the increase in motor efficiency outweigh the extra weight, complexity, cost and friction losses of a gearbox?

    And don’t ask an ‘EV transmission maker’, because then you’ll know the answer already. Ask an EV maker. All current EV makers have answered the question with a ‘no’.

    The street and the racetrack are different worlds, so you might get different answers to the same question.

    1. ModernMarvelFan says:

      “Whether an EV needs a gearbox you need to answer a simple question:: does the increase in motor efficiency outweigh the extra weight, complexity, cost and friction losses of a gearbox?”

      It is great question! That is the type of question that a good system engineer would have to answer.

      2 speed gearbox shouldn’t be too bad in terms of efficiency compared with a fixed speed gearbox.

      The cost should be low as well. But the size and weight will be slightly bigger. However, it will make the motor design easier and certainly easier on the motor drives…

  6. Bill Howland says:

    If a mopar with a smaller ICE can beat a Tesla by 6 seconds, then at these speeds an overdrive gear in the Tesla would greatly help efficiency without adding too much mechanical complication.

    Teslas, both the Roadster and S at high speeds were screamers, and due to the low-powerfactor of the old-fashioned induction motor at these speeds, made the drive inverter low efficiency, and the motor even more inefficient than it already is.

    Modern motors do not have any rotor losses as the Teslas do simply for the reason they have no rotor currents.

    A six second improvement from a smaller ICE should tend to indicate there is room for improvement.